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ARTICLES
THE LANCET • Published online May 7, 2003 • http://image.thelancet.com/extras/03art4453web.pdf
1
Summary
Background Health authorities worldwide, especially in the
Asia Pacific region, are seeking effective public-health
interventions in the continuing epidemic of severe acute
respiratory syndrome (SARS). We assessed the epidemiology
of SARS in Hong Kong.
Methods We included 1425 cases reported up to April 28,
2003. An integrated database was constructed from several
sources
containing
information
on
epidemiological,
demographic, and clinical variables. We estimated the key
epidemiological distributions: infection to onset, onset to
admission, admission to death, and admission to discharge.
We measured associations between the estimated case
fatality rate and patients’ age and the time from onset to
admission.
Findings After the initial phase of exponential growth, the
rate of confirmed cases fell to less than 20 per day by April
28. Public-health interventions included encouragement to
report to hospital rapidly after the onset of clinical
symptoms, contact tracing for confirmed and suspected
cases, and quarantining, monitoring, and restricting the
travel of contacts. The mean incubation period of the disease
is estimated to be 6·4 days (95% CI 5·2–7·7). The mean
time from onset of clinical symptoms to admission to
hospital varied between 3 and 5 days, with longer times
earlier in the epidemic. The estimated case fatality rate was
13·2% (9·8–16·8) for patients younger than 60 years and
43·3% (35·2–52·4) for patients aged 60 years or older
assuming a parametric distribution. A non-parametric
method yielded estimates of 6·8% (4·0–9·6) and 55·0%
(45·3–64·7), respectively. Case clusters have played an
important part in the course of the epidemic.
Interpretation Patients’ age was strongly associated with
outcome. The time between onset of symptoms and admission
to hospital did not alter outcome, but shorter intervals wil